Miniaturized and invisible laser-inscribed photonic circuits

Band gap changes in crystals and glasses locally induced by femtosecond laser pulses could lead to new invisibility and miniaturized applications. We found that the femtosecond-laser-induced band-gap shift (FLIBGS) has an exponential impact on the refractive index change in the transparent region of the spectrum near the electronic resonance absorption edge. Using the FLIBGS, we theoretically and experimentally demonstrated 3D waveguides with submillimeter bend radii, single-scan fabrication of waveguides in a crystal and a new concept of direct inscription of invisible structures.